The invention relates to a fan unit, in particular for an air conditioning system of a motor vehicle, comprising an electric motor for driving a fan wheel, an electronic device which generates waste heat and provides electrical current to the electric motor and a fan housing, wherein the fan wheel is disposed together with the electric motor in an air guiding region delimited by the fan housing.
Fan units of the aforementioned kind are known from prior art. They are frequently used in air conditioning systems for motor vehicles. The fan unit comprises the electric motor, the electronic device and the fan housing. The electric motor serves thereby to drive a fan wheel which is operatively connected to a rotor of the electric motor. The electronic device supplies the electric motor with electrical current or respectively operates said motor in open- and/or closed-loop control. In this respect, the electronic device particularly has power electronics at its disposal. The fan housing accommodates at least zonally, in particular completely, the fan wheel as well as the electric motor. Provision is thereby made for the fan wheel and the electric motor to be located in the air guiding region delimited by the fan housing. In an operation of the fan unit, air passes through the air guiding region, wherein the fan wheel driven by the electric motor serves to convey the air and therefore to generate an air flow through the fan housing.
The electronic device generates heat while operating the fan unit, which must be led away in the form of waste heat in order to keep the electronic device below or at a maximum temperature. It is known, for example, from prior art to provide the electronic device with a heat sink and to dispose said device in the air flow generated by the fan wheel. During the operation of the fan unit, the air delivered through the air guiding region then flows over the electronic device and therefore cools the same. The heat sink can comprise surface enlarging and/or vortex generating elements, for example ribs, knobs or the like, to increase the heat transfer. The German patent specification DE 10 2008 042 897 A1, for example, describes a fan device for a motor vehicle. Said fan device comprises a regulating device and a motor for actuating a ventilation device of the fan device. The fan device is designed such that the motor and the regulating device can be cooled by a common air flow of the ventilation device. The regulating device comprises a heat sink apparatus having a knobbed surface, wherein the regulating device is disposed in a receptacle of a housing section of the fan device such that the air flow of the ventilation device can flow to the heat sink apparatus or respectively said heat sink apparatus can be cooled.
The air flow delivered by the fan unit is frequently drawn in from an area outside of the motor vehicle. Liquid or rather moisture and dirt, for example dust and sand, are thus transported via said air flow into the fan housing. Due to temperature differences, liquid in the form of condensation can also additionally form, which then, for example, accumulates in the form of drops in regions of the fan housing, in particular at corners or ribs. That means however that the electronic device in the known embodiment from prior art has to be permanently protected from the ingress of moisture or dirt by means of an additional sealing element. At the same time, the sealing element cannot however substantially impair the cooling by means of the air flow. Due to the effects of ageing, in particular as a result of mechanical stress, temperature differences and the like, the danger then exists that moisture and/or dirt can penetrate through the seal and therefore to the electronic device. In certain circumstances, this leads to damage to or errors in the fan unit, in particular to short circuits or malfunctions in the electronic device and respectively the electric motor, or to said electronic device burning out.